1. Field of Invention
The present invention relates to a hydraulic flow rate measuring device and more particularly to a flow meter which determines the rate of flow from the amount of torque generated on a member of the device located in the stream of a flowing hydraulic.
2. Prior Art
One known type of flow rate meter is constructed with a suspended and movable target surface exposed to the stream of a flowing liquid. This type of flow rate meter has the disadvantage that during low volume liquid flow, a large percentage of the kinetic energy from the flowing liquid is expended to move the target, thereby rendering an inaccurate reading of the flow rate. Meter constructions sufficiently rugged to handle heavy flow rates, on the other hand, may be lacking in sensitivity to provide an accurate reading of slow liquid flow rates. Furthermore, a movable target exposed to the stream of a flowing liquid is subject to excessive wear so that replacement or maintenance of parts is frequently required. Representative but nonexhaustive of the prior art in the aforementioned type of flow measuring device are U.S. Pat. Nos. 2,600,309 and 3,559,197.
Heretofore, flow rate meters have been constructed as separate units including an open ended cylindrical housing providing fluid passage therethrough and in which the target is mounted to measure the flow rate. These units are inserted in a pipeline to measure the flow therein.
One embodiment of the present invention provides for a slight modification of an existing flow control valve in a pipeline as for example, a butterfly valve so that it serves as a flow rate measuring device and a flow control valve.